This invention relates to an ultrasonic nebulizer and more particularly to the oscillator circuit for driving the piezo-electric vibrator.
In an ultrasonic liquid nebulizer of conventional type, it is usual to drive the piezo-electric vibrator by a driving circuit constituted of a transistor oscillation circuit. Ultrasonic waves are generated to nebulize liquids, such as water, by the oscillation energy of the piezo-electric vibrator. Various conventional oscillator circuits have been employed. Generally, when the driving output is variable to regulate the nebulizing rate, the circuit is provided with a resistor connected in series with the bias resistor to vary the bias current for the transistor. However, a large base current of the transistor is often required with the bias resistor having a resistance of 1000 ohms to 3000 ohms and a capacity of approximately 2 watts, e.g., requiring a special variable resistor, thus making it difficult to regulate the driving output.
This invention eliminates such disadvantage. An ultrasonic nebulizer driving circuit according to the invention requires a reduced capacity for the bias resistor and facilitates regulation of the driving output by positive feedback, of a part of the high frequency energy at the piezo-electric vibrator, to the base of the transistor.
Explanation will be made hereinafter of an ultrasonic nebulizer driving circuit embodying the present invention referring to the attached drawings .